The present invention relates to a method for increasing the efficiency of gene transfer into target cells. The method permits efficient transformation of target cells in various technical fields such as medical science, cell technology, genetic engineering and developmental technology and a series of techniques relating thereto.
Owing to understanding in mechanisms of many human diseases as well as rapid progress in recombinant DNA technology and gene transfer technology, recently, protocols for somatic gene therapy have been developed for treating severe genetic diseases. In addition, currently, activities have been attempted to apply gene therapy to not only treatment of genetic diseases but also treatment of viral infections such as AIDS and cancers.
Almost all the gene transfer experiments in human being heretofore approved by Food and Drug Administration (FDA) are transduction of cells by recombinant retroviral vectors. Retroviral vectors can efficiently transfer a required exogenous gene into cells to stably integrate the exogenous gene into chromosomal DNA and therefore, especially, they are preferred gene transfer means for gene therapy wherein long term gene expression is desired. Such vectors are designed in various ways to avoid any adverse effect on transduced organisms. For example, replication functions of vectors are lost to prevent unlimited repetition of infection (transduction) due to auto-replication of the vectors to be used for gene transfer into cells. Since these vectors (replication deficient retroviral vectors) have no capability of auto-replication, in general, retroviral vectors packaged in viral particles are prepared by using retrovirus producer cells (packaging cells).
On the other hand, bone marrow cells are a good target for somatic gene therapy because bone marrow cells are easily manipulated in vitro and contain hematopoietic stem cells capable of auto-replication. Alternatively, human cord blood has previously also been demonstrated to contain a large number of primitive progenitor cells including hematopoietic stem cells. When gene therapy is carried out by gene transfer into these target cells and grafting thereof in a living body, the gene thus transferred is expressed over long term in blood cells to effect lifelong cures for disease.
However, in spite of intensive studies by various groups, hematopoietic stem cells are one of those whose efficient transduction is difficult. Heretofore, a most efficient gene transfer protocol relating to hematopoietic stem cells of mouse and other animals was co-culture of hematopoietic stem cells with retrovirus producer cells. However, for clinical gene therapy of human being, cell-free transduction is more desirable due to concerns about bio-safety. Unfortunately, efficient gene transfer into hematopoietic stem cells has generally not been possible without co-culture with retrovirus producer cells.
Recently, it has been reported that the gene transfer efficiency by retroviruses can be improved by a component of an extracellular matrix, fibronectin, or its fragments alone (J. Clin. Invest., 93, pp. 1451-1457 (1994); Blood, 88, pp. 855-862 (1996)). In addition, it has also been disclosed that fibronectin fragments produced by genetic engineering have the same properties and, by utilizing them, efficient transfer of an exogenous gene into hematopoietic stem cells can be carried out (WO 95/26200). Binding of a heparin binding domain of fibronectin to a retrovirus is suggested to be concerned in such improvement of the gene transfer efficiency by fibronectin. In all these methods utilizing fibronectin and fibronectin fragments, cells are infected with retroviruses in plates on which fibronectin or its fragment is immobilized.
The above-described gene transfer methods utilizing fibronectin and fibronectin fragments are considered to be achieved by fibronectin or its fragment molecules having both retrovirus binding domain and target cell binding domain on the same molecule (Nature Medicine, 2, pp. 876-872 (1996)). Therefore, for efficient gene transfer into various target cells by using the above-described method, it is necessary to prepare a functional material having both virus and target cell binding domains on one molecule according to respective particular cells and a problem still remains in the use thereof as a general gene transfer method.
Further, the above-described gene transfer method is carried out by immobilizing fibronectin or a fibronectin fragment on the surface of a plate to be used for culture of target cells upon infection of retroviruses. However, complicated procedures are required for immobilization on a plate and this is far from saying a simple and convenient gene transfer method.
Moreover, the functional material to be used in the above-described gene transfer method is limited to that containing a heparin binding domain derived from fibronectin as a retrovirus binding domain. Then, there are possibilities that an improved gene transfer method can be developed by finding out any other retrovirus binding substance.
The object of the present invention is to solve the problem and to provide a more convenient and efficient gene transfer method.
The present inventors have found that retrovirus infection by a functional material, typically, fibronectin or its fragment, can be promoted, even when a region having a retrovirus binding domain and a region having a cell binding domain are not present on the same molecule. That is, the present inventors have found that the efficiency of gene transfer into target cells by retroviruses can be improved by using an effective amount of a functional material containing a retrovirus bonding domain admixed with a functional material having a target cell binding domain.
In addition, the present inventors have also found that retrovirus infection enhancing activity by a functional material can be observed even when the functional material is not immobilized on a surface of a plate. The present inventors have further found that the efficiency of gene transfer into target cells can be improved by contacting retroviruses with the target cells in the presence of a functional material immobilized on beads.
In addition, the present inventors have further found a retrovirus binding substance which does not contain a heparin binding domain derived from fibronectin and also found that the material and derivatives thereof are useful for gene transfer into target cells with retroviruses. Moreover, the present inventors have succeeded in creation of functional materials useful for gene transfer into target cells with retroviruses. Thus, the present invention has been completed.
Then, the first aspect of the present invention relates to a method for increasing the efficiency of gene transfer into target cells with retroviruses. The method is directed to transduction of target cells with a retrovirus and is characterized by infecting the target cells with the retrovirus in the presence of a mixture of an effective amount of a functional material having retrovirus binding domain, and an effective amount of another functional material having target cell binding domain to permit transfer of the gene into the target cells.
The functional material having retrovirus binding domain used in the first aspect of the present invention is not specifically limited and, for example, it is a functional material selected from the group consisting of the Heparin-II binding domain of fibronectin, a fibroblast growth factor, a collagen, a polylysine and functional equivalents thereof. The functional material having target cell binding domain may be a substance containing a ligand which can bind to target cells. As the ligand, there are cell adhesion proteins, hormones, cytokines, antibodies, sugar chains, carbohydrates and metabolites of target cells and the like. Examples of adhesion proteins include polypeptides of a cell binding domain of fibronectin. As the cell binding domain of fibronectin, there are polypeptides of binding domain to VLA-5 and/or VLA-4. Further, other examples of ligand include erythropoietin.
The functional material to be used in the first aspect of the present invention may be used without immobilization or may be immobilized and, when they are immobilized on beads, they can be used conveniently. In addition, when a ligand specific for target cells is selected as the functional material having target cell binding domain, the first aspect of the present invention permits convenient transduction of intended target cells.
As described above, in the conventional methods as disclosed in WO 95/26200 and Nature Medicine, it is consider to be an essential mechanism for improving the gene transfer efficiency into target cells with a retrovirus to co-localize the retrovirus and the target cells on a functional material having both retrovirus binding domain and target cell binding domain on the same molecule. However, according to the present invention, the efficiency of gene transfer into target cells can be improved by carrying out gene transfer into the target cells with a retrovirus in the presence of a mixture of an effective amount of a functional material having retrovirus binding domain and an effective amount of another functional material having target cell binding domain.
The second aspect of the present invention relates to a culture medium for target cells to be used for gene transfer into the target cells with retroviruses which comprises a mixture of an effective amount of a functional material having retrovirus binding domain, and an effective amount of another functional material having target cell binding domain.
By using the culture medium of the second aspect of the present invention, the first aspect of the present invention can be carried out conveniently.
The third aspect of the present invention relates to a localization method of retroviruses and the method is characterized by incubating a culture medium containing a retrovirus contacted with a mixture of an effective amount of a functional material having retrovirus binding domain, and an effective amount of another functional material having target cell binding domain.
The fourth aspect of the present invention relates to a kit to be used for carrying out retrovirus-mediated gene transfer into target cells and the kit comprises:
(a) an effective amount of a functional material having retrovirus binding domain and/or an effective amount of another functional material having target cell binding domain;
(b) an artificial substrate for incubating target cells and a retrovirus; and
(c) a target cell growth factor for pre-stimulating the target cells.
By using the reagent kit of the fourth aspect of the present invention, the first and third aspect of the present invention can be carried out conveniently.
The fifth aspect of the present invention relates to a method for improving the gene transfer efficiency into target cells with retroviruses and the method is characterized by infecting the target cells with a retrovirus in the presence of an effective amount of a functional material having a target cell binding domain as well as a retrovirus binding domain derived from a fibroblast growth factor, a collagen or a polylysine, or a functional equivalent thereof on the same molecule to permit transduction of the target cells.
In the above conventional methods as described in WO 95/26200 and Nature Medicine, fibronectin fragments are disclosed as the material which can be used in a most efficient method for improving gene transfer into target cells with retroviruses. However, regarding functional materials other than fibronectin fragments, there is no specific disclosure about what kind of a functional material can be used in an efficient method for gene transfer into target cells with retroviruses. More specifically, in the conventional method, only the repeat 12-14 of fibronectin is disclosed as the retrovirus binding domain.
The present inventors have unexpectedly found that a fibroblast growth factor, a collagen, a polylysine and so on which do not have any structural relation to the repeat 12-14 of fibronectin can be effectively used in a method for improving gene transfer into target cells with retroviruses. Therefore, any functional equivalent of these materials, i.e., any material which has a retrovirus binding domain functionally equivalent to these materials and can improve the gene transfer efficiency into target cells with retrovirus can be used in the fifth aspect of the present invention.
In the fifth aspect of the present invention, as the target cell binding domain, a material having a ligand which can bind to target cells can be used and this material is coupled to the retrovirus binding domain.
Examples of the ligand include cell adhesion proteins, hormones, cytokines, antibodies, sugar chains, carbohydrates, metabolites of target cells and the like. Examples of cell adhesion proteins include polypeptides of a cell binding domain of fibronectin. For example, polypeptides of binding domain to VLA-5 and/or VLA-4 can be used in the present invention. Further, other examples of ligand include erythropoietin.
In the fifth aspect of the present invention, as the fibroblast growth factor to be used as the retrovirus binding domain, there are fibroblast growth factors selected from, for example, a fibroblast growth factor represented by SEQ. ID No. 3 of the Sequence Listing, functional equivalents of the factor and polypeptides containing the factor or functional equivalents thereof.
Examples of these functional materials include polypeptides containing an amino acid sequences represented by SEQ. ID Nos. 4 and 5 of the Sequence Listing.
In the fifth aspect of the present invention, collagens to be used as the retrovirus binding domain include, for example, collagens selected from a collagen fragment containing an insulin binding domain derived from type V collagen, functional equivalents of the fragments and polypeptides containing the fragments or functional equivalents thereof. In addition, examples of the fragments include a fragment containing an amino acid sequence represented by SEQ. ID No. 6 of the Sequence Listing.
Examples of these functional materials include polypeptides represented by SEQ. ID Nos. 7 and 8 of the Sequence Listing.
In the fifth aspect of the present invention, the polylysine to be used as the retrovirus binding domain is a polymer of L-lysine and, for example, one having a suitable polymerization degree can be selected from commercially available products and used.
If the retrovirus binding domain derived from a fibroblast growth factor, a collagen or a polylysine has a target cell binding domain, simultaneously, the gene transfer efficiency into target cells with a retrovirus can be improved by infecting the target cells with the retrovirus in the presence of an effective amount of the retrovirus binding domain derived from the fibroblast growth factor, the collagen or the polylysine. If target cells are adhesion cells, a retrovirus and target cells respectively bind to and adhere to the functional material, and the gene transfer efficiency into the target cells with the retrovirus can be improved by infecting the target cells with the retrovirus in the presence of an effective amount of the retrovirus binding domain derived from the fibroblast growth factor, the collagen or the polylysine.
It has also been found that, if a polypeptide represented by SEQ. ID No. 1 of the Sequence Listing (hereinafter referred to as H-271) has a target cell binding domain, simultaneously, that is, if target cells bind to the polypeptide, H-271, the gene transfer efficiency into the target cells with a retrovirus can be improved by infecting the target cells with the retrovirus in the presence of an effective amount of the polypeptide.
That is, although the retrovirus binding domain disclosed in the above Nature Medicine is only the repeat 12-14 of fibronectin, the present inventors have unexpectedly found that this H-271 effectively acts as a target cell binding domain according to a particular kind of target cells to improve the gene transfer efficiency into the target cells. In addition, in case that target cells are adhesion cells, the target cells and a retrovirus bind and adhere to the polypeptide, respectively, and the gene transfer efficiency into the target cells with the retrovirus can be improved by infecting the target cells with the retrovirus in the presence of an effective amount of the polypeptide.
In the fifth aspect of the present invention, the functional material may be used without immobilization or may be immobilized, though immobilization is preferred in case that target cells are adherent cells.
The sixth aspect of the present invention relates to a culture medium for target cells to be used for gene transfer into the target cells with a retrovirus which comprises an effective amount of a functional material which has a target cell binding domain as well as a retrovirus binding domain derived from a fibroblast growth factor, a collagen or a polylysine, or a functional equivalent thereof on the same molecule.
The seventh aspect of the present invention relates to a localization method of a retrovirus which comprises incubating a culture medium containing the retrovirus contacted with a effective amount of a functional material containing a retrovirus binding domain derived from a fibroblast growth factor, a collagen or a polylysine. These functional materials can be efficiently used in localization of a retrovirus for improvement of gene transfer into target cells with the retrovirus.
Moreover, the localization method of a retrovirus of the present invention include incubation of the retrovirus contacted with an effective amount of a functional material comprising a target cell bind domain as well as a retrovirus binding domain derived from a fibroblast growth factor, a collagen or a polylysine, or a functional equivalent thereof on the same molecule.
The eighth aspect of the present invention is a kit to be used for carrying out retrovirus-mediated gene transfer into target cells and the kit comprises:
(a) an effective amount of a functional material having a retrovirus binding domain as well as a target cell binding domain derived from a fibroblast growth factor, a collagen or a polylysine or a functional equivalent thereof on the same molecule;
(b) an artificial substrate for incubating target cells contacted with a retrovirus; and
(c) a target cell growth factor for pre-stimulating the target cells.
For practicing any method of the first and fifth aspects, any culture medium of the second and sixth aspects, any method of the third and seventh aspects and any kit of the fourth and eighth aspects of the present invention, the functional materials immobilized on beads can be suitably used.
The ninth aspect of the present invention relates to a method for improving the gene transfer efficiency into target cells with a retrovirus and characterized in that the target cells are infected with the retrovirus in the presence of an effective amount of a functional material immobilized on beads selected from substantially pure fibronectin, a substantially pure fibronectin fragment or a mixture thereof to permit transduction of the target cells with the retrovirus.
The tenth aspect of the present invention also relates to a method for improving the gene transfer efficiency into target cells with a retrovirus and characterized in that the target cells are infected with the retrovirus in the presence of an effective amount of a functional material selected from substantially pure fibronectin, a substantially pure fibronectin fragment or a mixture thereof without immobilization to permit transduction of the target cells with the retrovirus.
In the above conventional methods as disclosed in WO 95/26200 and Nature Medicine, it is an essential mechanism for improving the gene transfer efficiency with a retrovirus that the retrovirus and the target cells should be co-localized on a functional material having a retrovirus binding domain and a target cell binding domain on the same molecule. In these methods, the co-localization of both retrovirus and target cells on the functional material having both retrovirus binding domain and target cell binding domain on the same molecule firstly becomes possible by immobilizing the functional material having the retrovirus binding domain and the target cell binding domain on the same molecule on a culture substrate.
However, according to the present invention, even when substantially pure fibronectin, a substantially pure fibronectin fragment or a mixture thereof is used, unexpectedly, the gene transfer efficiency into target cells with a retrovirus can be efficiently improved by using the functional material having both retrovirus binding domain and target cell binding domain on the same molecule without immobilization on a culture substrate.
As the target cells to be used in the first, fifth, ninth and tenth aspects of the present invention, there can be used, for example, cells selected from stem cells, hematopoietic cells, non-adherent low density mononuclear cells, adherent cells, bone marrow cells, hematopoietic stem cells, peripheral blood stem cells, umbilical blood cells, fetal hematopoietic stem cells, embryoplastic stem cells, embryonic cells, primordial germ cells, oocyte, oogonia, ova, spermatocyte, sperm, CD34+ cells, c-kit+ cells, multipotential hemopoietic progenitor cells, unipotential hemopoietic progenitor cells, erythrocytic precursor cells, lymphocytic precursor cells, mature blood cells, lymphocytes, B cells, T cells, fibroblast, neuroblast, nerve cells, endothelial cells, angio-endothelial cells, hepatic cells, myoblast, skeletal muscle cells, smooth muscle cells, cancer cells, myeloma cells and leukemia cells.
As the retrovirus to be used in the first, third, fifth, seventh, ninth and tenth aspects of the present invention, a retrovirus containing an exogenous gene can be used and the retrovirus may be, for example, a recombinant retroviral vector. Further, the retrovirus may be, for example, a replication deficient recombinant retroviral vector.
The eleventh aspect of the present invention relates to transduced cells obtained by the first, fifth, ninth or tenth aspect of the present invention.
The twelfth aspect of the present invention relates to a cell grafting method for grafting the transduced cells of the eleventh aspect of the present invention into a vertebrate animal.
The thirteenth aspect of the present invention relates to a polypeptide represented by SEQ. ID No. 13 of the Sequence Listing which can improve the gene transfer efficiency into target cells with a retrovirus, or functional equivalents thereof.
The fourteenth aspect of the present invention relates to a gene encoding the polypeptide of the thirteenth aspect of the present invention. Examples of the gene include a gene represented by SEQ. ID No. 17 of the Sequence Listing or a gene which can hybridize to the above gene under stringent conditions and encode a polypeptide which can improve the gene transfer efficiency into target cells with a retrovirus.
In the above conventional methods of WO 95/26200 and Nature Medicine, the most efficiency peptide to be used for the gene transfer is CH-296. On the other hand, the present inventors have unexpectedly found that the same polypeptide without VLA-5 binding domain and VLA-4 binding domain can be used in the present invention.
The fifteenth aspect of the present invention relates to a polypeptide represented by SEQ. ID No. 30 of the Sequence Listing which can improve a gene transfer efficiency into target cells with a retrovirus, or its functional equivalent.
The sixteenth aspect of the present invention relates to a gene encoding the polypeptide of the fifteenth aspect of the present invention. Examples of the gene includes a gene represented by SEQ. ID No. 33 of the Sequence Listing of a gene which can hybridize to the above gene under stringent conditions and encode a polypeptide which can improve the gene transfer efficiency into target cells with a retrovirus.
The seventeenth aspect of the present invention relates to a polypeptide represented by SEQ. ID No. 5 which can improve the gene transfer efficiency into target cells with a retrovirus, or functional equivalents thereof.
The eighteenth aspect of the present invention relates to a gene encoding the polypeptide of the seventeenth aspect of the present invention. Examples of the gene include a gene represented by SEQ. ID No. 26 or a gene which can hybridize to the above gene and encode a polypeptide which can improve the gene transfer efficiency into target cells with a retrovirus.
For the gene transfer method of the present invention, usually, recombinant retroviral vectors are used and, in particular, a replication deficient retroviral vector is suitable. The capability of replication of the vector is lost to prevent auto-replication in infected cells, so the vector is non-pathogenic. These vectors can invade into host cells such as vertebrate animal cells, in particular, mammalian cells to stably integrate exogenous genes inserted into the vectors in chromosomal DNA of host cells.
In the present invention, an exogenous gene to be transferred into cells can be used by inserting it into a retroviral vector under the control of a suitable promoter, for example, a promoter of LTR present in a retrovirus or an exogenous promoter. In addition, in order to achieve transcription of an exogenous gene, other regulatory elements which can cooperate with a promoter and a transcription initiation site, for example, an enhancer, can also be present in a vector. Moreover, preferably, an inserted gene can have a terminator sequence at its downstream. The exogenous gene to be transferred into cells can be natural or artificial ones, and can have additional DNA molecule derived from heterologous sources coupled thereto by ligation or other means known to the art.
The exogenous genes inserted into a retrovirus can be any genes of interest for transduction of the cells. For example, the exogenous genes can encode an enzyme which is associated with a disorder to be treated, a protein, an antisense nucleic acid, a ribozyme or a false primer (see, e.g. WO 90/13641), an intracellular antibody (see, e.g. WO 94/02610), a growth factor or the like.
The retroviral vectors to be used in the present invention can have a marker gene so that transducer cells can be readily selected. As the marker gene, for example, a drug resistant gene which provides transformant cells with antibiotic resistance or a reporter gene which provides transformant cells with an enzyme activity for detection thereof can be used.
As the vectors to be used, there are retroviral vectors such as known MFG vector (ATCC No. 68754), xcex1-SGC (ATCC No. 68755) and the like. In addition, both N2/ZipTKNEO vector (TKNEO, Blood, Vol. 78, pp. 310-317 (1991)) and PM5neo vector (Exp. Hematol., Vol. 23, pp. 630-638 (1995)) used in the examples hereinafter contain neomycin resistant genes (neomycin phosphotransferase gene) as their marker genes. Then, cells transformed with these vectors can be recognized as cells having resistance to antibiotics (neomycin, G418, etc.) which are inactivated by the gene products. Moreover, these vectors can be prepared as virus particles containing the vectors packaged therein by using known packaging cell strains, for example, PG13 (ATCC CRL-10686), PG13/LNc8 (ATCC CRL-10685), PA317 (ATCC CRL-9078), cell strains described in U.S. Pat. No. 5,278,056, GP+E-86 (ATCC CRL-9642), GP+envAm-12 (ATCC CRL-9641) and the like.
The term xe2x80x9ceffective amountxe2x80x9d of the functional material used herein means the amount required for transformation of target cells in gene transfer to target cells with a retrovirus. The amount can be selected depending upon a particular functional material, a retrovirus and a particular kind of target cells by using the method described herein. The term xe2x80x9cthe gene transfer efficiencyxe2x80x9d used herein means the transformation efficiency.
The capability of binding to retroviruses of the functional material, i.e., effectiveness and usefulness of the functional material in the present invention can be ascertained by routine assays as disclosed in Examples hereinafter.
These assays determine the extent to which retrovirus particles are bound to the functional material immobilized to the matrix to be used in the present invention so as to resist washing from the matrix. Briefly, for example, a virus-containing supernatant can be incubated in a well containing the immobilized functional material having a retrovirus binding domain. The well is then thoroughly washed with a physiological saline buffer and thereafter, target cells are incubated in the well to determine the level of infectious activity of the virus remaining in the well. The reduction in infectious activity, or titer, relative to the initial viral supernatant is assessed and compared to that of a similar control (e.g. using a BSA-coated well). A significantly higher titer remaining in the functional material containing well as compared to the control well indicates that the material can be used as the functional material in the present invention.
To facilitate this screening procedure, the viral vector can contain a selectable marker gene.
The functional material having retrovirus binding domain to be used in the present invention can be screened by these assays.
As such a functional material having retrovirus binding domain, there is a functional material which has a retrovirus binding domain derived from Heparin-II binding domain of fironectin, a fibroblast growth factor, a collagen or a polylysine.
The binding of a cell binding domain of the functional material to be used in the present invention to cells, i.e., binding of a material containing a target cell binding ligand to cells can likewise be assayed using conventional procedures. For example, such procedures include those described in Nature 352: 438-441 (1991).
Briefly, the functional material having cell binding domain is immobilized on a culture plate and the cell population to be assayed is overlaid in a medium, followed by incubation for 30 minutes to 2 hours. After this incubation period, cells non-adherent to the functional material are retrieved, counted and assayed for viability. Cells adherent to the functional material are also retrieved using trypsin or cell dissociation buffer (e.g. Gibco), counted and viability tested. In some cases, for example for hematopoietic colony forming cells, the cells are further cultured for an additional 12 to 24 days to ascertain the colony forming characteristics of the cells. The percentage of adherent cells is then calculated and compared to a standard or standard control such as bovine serum albumin (BSA) immobilized on a culture plate. Substantial binding of the target cells to the assayed functional substance provides an indication that the functional material/cell combination is suitable for the present invention and the functional material having cell binding domain can co-exist with or be coupled to the functional material having retrovirus binding domain, followed by assessing retrovirus infection of the target cells to construct the functional material to be used in the present invention.
As the functional material having retrovirus binding domain which can be used in the present invention, as described above, there is a functional material which has a retrovirus binding domain derived from Heparin-II binding domain of fironectin, a fibroblast growth factor, a collagen or a polylysine. All substances which have a retrovirus binding domain equivalent to the above and can improve the gene transfer efficiency into target cells with retroviruses by coupling to or co-existing with a ligand having target cell binding domain are included in the functional equivalents to the retrovirus bonding domain derived from a fibroblast growth factor, a collagen or a polylysine.
The effective amount of the functional material(s) to be used in the present invention can be determined by using target cells and a retrovirus in the gene transfer method of the present invention in the presence of the selected functional material having retrovirus binding domain coupled to or coexisting with the functional material having target cell binding domain and assessing improvement of the gene transfer efficiency according to the above-described method.
Hereinafter, the present invention will be illustrated in detail.
One aspect of the present invention is a method for improving the gene transfer efficiency into target cells with a retrovirus. This method is characterized by infecting viable target cells with a retrovirus in the presence of a mixture of the functional material having retrovirus binding domain and the functional material having target cell binding domain which is effective for improving the gene transfer efficiency into the target cells with the retrovirus.
This method can be used for obtaining transformant cells transduced with the retrovirus and grafting the cells into an individual organism permits gene transfer into an individual organism.
The functional material having retrovirus binding domain to be used in this method is not specifically limited and examples thereof include Heparin-II binding domain of fibronectin, a fibroblast growth factor, a collagen, a polylysine and the like. Likewise, functional equivalents thereof, for example a functional material having a heparin binding domain can also be used. In addition, a mixture of the functional materials, a polypeptide containing the functional material, a polymer of the functional material, a derivative of the functional material and the like can also be used. These functional materials can be obtained from naturally occurring products, or artificially produced (e.g., produced by genetic engineering techniques or chemical syntheses). Further, they can be produced by combining naturally occurring products with artificial products.
In so far as the retrovirus binding domain and/or target cell binding domain which can achieve gene transfer with the high efficiency as described herein are maintained, the functional material to be used may be those having mutation in amino acid sequences of naturally occurring polypeptides. In the present invention, even if deletion, substitution, insertion and/or addition of one or plural, for example, up to several amino acids are present in the amino acid sequences of naturally occurring polypeptides, in so far as the desired retrovirus binding domain and/or target cell binding domain are maintained such polypeptides are referred to as functional equivalents of the polypeptides having naturally occurring amino acid sequences. These functional equivalents can be obtained by preparing genes encoding the functional equivalents to produce the equivalents and ascertaining their biological activities.
In this regard, the pertinent biotechnology arts have already advanced to a state in which the deletion, substitution, addition or other modifications of amino acids in the required functional domains can be routinely carried out. Then, the resultant amino acid sequences can be routinely screened for the desired cell binding activity or virus binding activity.
A gene encoding the functional equivalent can be obtained by searching for genes hybridizable to the gene encoding the above functional material.
That is, the gene encoding the above functional material or a part of its nucleotide sequence can be used as a probe of hybridization or primers of a gene amplification method such as PCR or the like to screen a gene encoding a protein having a similar activity to the functional material. Sometimes, in this method, a DNA fragment containing only a part of the desired gene is obtained. In such case, after ascertaining that the resultant DNA fragment is a part of the desired gene, the whole desired gene can be obtained by carrying out hybridization with the DNA fragment or a part thereof as a probe or carrying out PCR with primers synthesized based on the nucleotide sequence of the DNA fragment.
The above hybridization can be carried out, for example, under the following conditions.
That is, a membrane on which DNA is immobilized is incubated in 6xc3x97SSC (1xc3x97SSC: 0.15M NaCl, 0.015M sodium citrate, pH 7.0) containing 0.5% of SDS, 0.1% of BSA, 0.1% of polyvinyl pyrrolidone, 0.1% of Ficoll 400 and 0.01% of denatured salmon sperm DNA together with a probe at 50xc2x0 C. for 12 to 20 hours. After completion of incubation, the membrane is washed with, firstly, 2xc3x97SSC containing 0.5% of SDS at 37xc2x0 C. and then with changing the concentrations of SSC to 0.1xc3x97SSC and temperatures to 50xc2x0 C. until the signal derived from the immobilized DNA can be distinguished from the background.
In addition, whether or not the resultant gene thus obtained is the desired one can be ascertained by examining the activity of the protein encoded by the resultant gene according to the above method.
As described in the above WO 95/26200, Heparin-II binding domain of fibronectin is the polypeptide having a retrovirus binding domain. Although a fibroblast growth factor, a collagen and a polylysine do not have any structural similarity to Heparin-II binding domain of fibronectin (e.g., similarity of amino acid sequences), the present inventors have found that these substances have retrovirus binding domains.
The functional material having target cell binding domain to be used in the present invention is not specifically limited, either, and is a substance having a ligand which can bind to target cells. Examples of the ligand include cell adhesion proteins, hormones, cytokines, antibodies against antigens on cell surfaces, polysaccharides, sugar chains in glycoproteins or glycolipids, metabolites of target cells and like. In addition, there can be used polypeptides containing the functional materials, polymers of the functional materials, derivatives of the functional materials, functional equivalents of the functional materials and the like. These functional materials can be obtained from naturally occurring products or artificially produced (e.g., produced by gene engineering techniques or chemical synthetic techniques). Further, they can be produced by combining naturally occurring products with artificially products.
Cell adhesion proteins to be used are, for example, fibronectin and its fragments. For example, the cell binding domain of human fibronectin which corresponds to Pro1239-Ser1515, as described in U.S. Pat. No. 5,198,423, has been shown to have the function equivalent to the polypeptide C-274 disclosed herein and to bind to cells including BHK and B16-Fl0 cells (Kimizuka et al., J. Biochem. Vol. 110, pp. 285-291 (1991)). A sequence composed of four amino acids of RGDS present in these polypeptides is a ligand for VLA-5 receptor. Expression of VLA-5 receptor is observed in a wide variety of cells and it is expressed in undifferentiated cells better than in differentiated cells. In addition, CS-1 region of fibronectin is known to be a ligand for VLA-4 receptor and binds to cells expressing the receptor (T cells, B cells, monocytes, NK cells, acidophiles, basophiles, thymocytes, myelomonocytic cells, erythroblastic precursor cells, lymphocytic precursor cells, melanoma, muscle cells and the like). The polypeptide described in JP-A 3-284700 and represented by SEQ. ID No. 29 (hereinafter referred to as C277-CS1) is a polypeptide having ligands for both above VLA-5 and VLA-4 receptors and can be used for gene transfer into cells having these receptors. Moreover, it has been shown that Heparin-II domain can bind to fibroblasts, endothelial cells and tumor cells. The polypeptide sequence of the cell binding domain of Heparin-II domain is useful for directing retrovirus infection toward targeted cells in the presence of a polypeptide of the functional material having retrovirus binding domain.
Hormones and cytokines having cell specific activities are suitable as the functional material having cell binding domain in the present invention. For example, erythropoietin which is a cytokine in the hematopoietic system can be used for gene transfer into erythrocytic cells. Erythropoietin can be prepared according to a known method and used. In addition, functional equivalents of the erythropoietin and polypeptides containing erythropoietin or functional equivalents thereof can also be used.
As described in Examples hereinafter, when the functional material having retrovirus binding activity (e.g., H-271 and a fibroblast growth factor) is used in admixed with C-274 which is a polypeptide having a cell binding activity derived from fibronectin or the like, the high gene transfer efficiency can be obtained. NIH/3T3 cells which are used in these experiments express VLA-5 receptor which can bind to C-274 and the interaction of them contribute to improvement of the gene transfer efficiency.
Further, the same phenomenon is also observed, when an erythropoietin derivative is present in gene transfer into TF-1 cells which express erythropoietin receptor (Blood, Vol. 73, pp. 375-380 (1989)). Moreover, this effect is not observed in cells which do not have any erythropoietin receptor.
From these results, it is clear that cell specific increase in the gene transfer efficiency takes place in the presence of the functional material having retrovirus binding domain together with the functional material having cell binding domain.
In this aspect of the present invention, the functional material having retrovirus binding domain is used in the form of a mixture with another functional material having target cell binding domain. Thereby, the gene transfer efficiency into target cells having affinity to the functional materials is remarkably improved. Since the gene transfer efficiency is improved, co-culture with virus producer cells can be avoided and this is one of advantages of the present invention.
Means for selective gene transfer into target cells has high utility and various studies have been done. For example, there is non-viral vector (molecular conjugation vector) wherein a material binding to a receptor present on a cell surface is coupled to a DNA binding material. Examples of gene transfer using such a vector include gene transfer into hepatoma cells with asialoglycoprotein (J. Biol. Chem., Vol. 262, pp. 4429-4432 (1987)), gene transfer into lymphoblasts with transferrin (Proc. Natl. Acad. Sci. USA, Vol. 89, pp. 6099-6103 (1992)), gene transfer into cancer cells with anti EGF receptor antibody (FEBS Letters, Vol. 338, pp. 167-169 (1994)) and the like. These gene transfer methods using non-viral vectors are undesirable from the viewpoint of long term gene expression of transferred genes because the transferred genes are not integrated into chromosomal DNA of cells. Activities have been attempted to use retroviruses which are widely used as vectors capable of insertion of genes into chromosomes to infect specific cells. For examples, gene transfer into hepatocytes by direct chemical modification of retroviruses to couple to lactose (J. Biol. Chem., Vol. 266, pp. 14143-14146 (1991)), gene transfer into erythropoietin receptor-expressing cells by utilizing recombinant viral particles having an envelope protein which is a fused protein with erythropoietin (Science, Vol. 266, pp. 1373-1376 (1994)) and the like have been developed. However, for this purpose, it is necessary to prepare special protein particles according to particular target cells. In addition, chemical modification of viral particles requires complicated procedures and is liable to inactivate viruses. Moreover, regarding a virus envelope modified by gene engineering, the desired product having required functions (binding to target cells and construction of viral particles) is not always obtained.
The above WO 95/26200 suggests that a retroviral vector without any special modification can be transferred into cells in the presence of a fibronectin fragment to which a suitable ligand having cell binding activity is covalently coupled. However, this method uses a functional molecule having both virus binding activity and cell binding activity and therefore an individual special functional material should be prepared according to particular kinds of cells. In addition, it is unknown whether or not the functional material prepared maintains both activities.
The combination of the functional material having retrovirus binding domain and the different functional material having target cell binding domain of the present invention can provide a gene delivery system using retroviruses for a wide variety of cell species. For this purpose, the functional material having retrovirus binding domain does not need to be covalently coupled to the functional material having cell binding domain. Therefore, there is no need to prepare an individual special functional material wherein the functional material having retrovirus binding domain is covalently coupled to the functional material having cell binding domain according to particular kinds of cells and gene transfer into target cells can be conveniently and efficiently carried out.
Examples of gene transfer into target cells using the method of the present invention is gene transfer into cells of the hematopoietic system. It has been known that the above CS-1 cell adhesion region of fibronectin is useful for gene transfer into hematopoietic stem cells. Further, it has also been known that, in addition to the above erythropoietin, various other cell specific cytokines are concerned in differentiation of hematopoietic cells, and gene transfer can be carried out specifically into target cells (cell lines) by utilizing them. For example, when G-CSF is used, megakaryoblasts and granulocytic precursor cells can be used as the target cells of transduction.
When using a substance which specifically or predominantly binds to malignant cells as the functional material having cell binding domain, gene transfer into such target cells can be carried out.
For example, it has been known that receptors named as HER-2 and HER-4 are expressed in certain breast carcinoma cells (Proc. Nat. Acad. Sci. USA, Vol. 92, pp. 9747-9751 (1995)). Accordingly, it is possible to control growth of breast carcinoma cells by combining heregulin which is a ligand for the receptors with the functional material having retrovirus binding domain.
In addition, by using the functional material containing iodine for thyroid (cancer) cells or the functional material containing a high-density lipoprotein (HDL), an asialoglycoprotein or a part thereof for liver (cancer) cells, these cells can be used as the target cells for transduction.
Further, by using antibodies against antigens present on cell surfaces, suitably, monoclonal antibodies as the functional material having cell binding activity, any cells whose antibodies are available can be used as target cells. Thus, a wide variety of cells can be used as the target cells by utilizing the localization method of a retroviral vector and target cells disclosed by the present invention.
In the particularly preferred aspect, the gene transfer efficiency into target cells with a retrovirus is increased by using a novel functional material.
Heretofore, only Heparin-II domain of fibronectin has been known to be the functional material having retrovirus binding domain effective for gene transfer into target cells with retroviruses.
As described above, the domain itself has that binding to certain cells and, in some cases, this activity is undesired depending upon certain target cells. In such cases, the desired results can be obtained by replacing the binding domain with another cell binding domain. In this manner, plural functional materials having different properties can be used and this makes broader application of the gene therapy according to the present invention possible and transduction of the intended target cells can be readily carried out.
The novel functional material having retrovirus binding domain provided by the present invention include fibroblast growth factors, polypeptides containing the factors, collagen fragments, a mixture of the fragments, polypeptides containing the fragments, polymers of the functional material and the like. Polylysines are also used for this purpose of the present invention. These functional materials can be obtained from naturally occurring products or can be artificially produced (e.g., produced by genetic engineering techniques or chemical syntheses). Further, they can be produced by combination of naturally occurring products and chemically synthesized products. The function material can be used for the gene transfer method of the first aspect of the present invention and chimera molecules of the functional material and the other functional material having cell binding domain are also useful for gene transfer.
All the above-described functional materials have retrovirus binding activity. However, these materials do not contain Heparin-II domain of human fibronectin described in WO 95/26200 or polypeptides having similar amino acid sequences.
As the fibroblast growth factor, a substantially purified naturally occurring product can be used or a product prepared by genetic engineering techniques can be used. In the present invention, the fibroblast growth factor, that is represented by SEQ. ID No. 3 of the Sequence Listing can be used and modified derivatives thereof maintaining functions of the polypeptide can also be used. Examples of fibroblast growth factor derivatives include a polypeptide represented by SEQ. ID No. 4 of the Sequence Listing (hereinafter referred to as C-FGAxe2x80xa2A). This is a polypeptide wherein the cell adhesion domain polypeptide of fibronectin is coupled to the N-terminal of a fibroblast growth factor represented by SEQ. ID No. 3 and can be produced by genetic engineering techniques as generally disclosed in U.S. Pat. No. 5,302,701. The polypeptide can be obtained by using E. coli which has been disclosed in the above U.S. Patent as FERM P-12637, and now deposited under Budapest Treaty with National Institute of Bioscience and Human-Technology (NIBH), Agency of Industrial Science and Technology, Ministry of International Trade and Industry of 1-1-3, Higashi, Tsukuba-shi, Ibaraki-ken, Japan, under the accession number of FERM BP-5278 (date of original deposit: Dec. 9, 1991).
A polypeptide derivative of the above C-FGFxe2x80xa2A having CS-1 cell adhesion domain derived from fibronectin which is represented by SEQ. ID No. 5 (hereinafter referred to as C-FGF-CS1) can be obtained by using Escherichia coli deposited under Budapest Treaty with the NIBH of 1-1-3, Higashi, Tsukuba-shi, Ibaraki-ken, Japan, under the accession number of FERM BP-5654 (date of original deposit; Sep. 6, 1996) according the process described herein. This C-FGF-CS1 is particularly useful for gene transfer into target cells having CS-1 binding property, in particular, hematopoietic stem cells.
As collagen fragments, substantially purified fragments obtained by enzymatically or chemically cleaving natural collagens can be used or those prepared by genetic engineering techniques can be used. In addition, modifications of these fragments maintaining their functions can be used. Among collagens, human type V collagen has strong insulin binding activity (JP-A 2-209899). An example of polypeptides having insulin binding domain is a polypeptide which contains an amino acid sequence represented by SEQ. ID No. 28 of the Sequence Listing (JP-A 5-97698), for example, a polypeptide represented by SEQ. ID No. 6 of the Sequence Listing (hereinafter referred to as ColV). ColV can be prepared according to a method disclosed in Examples herein. A polypeptide which contains ColV and represented by SEQ. ID No. 7 (hereinafter referred to as C277-ColV) is the polypeptide wherein the cell adhesion domain polypeptide of fibronectin is coupled to the N-terminal of ColV and can be produced by genetic engineering technique according to JP-A 5-97698 as described above. C277-ColV can be obtained by using E. coli which is disclosed under the accession number of FERM P-125690 in JP-A 5-97698 and deposited under Budapest Treaty with NIBH of 1-1-3, Higashi, Tsukuba-shi, Ibaraki-ken, Japan, under the accession number of FERM BP-5277 (date of original deposit: Oct. 7, 1991).
A polypeptide (hereinafter referred to as C-ColV-CS1) derived from C277-ColV which is represented by SEQ. ID No. 8 and has CS-1 cell adhesion domain derived from fibronectin can be prepared as followed. A DNA fragment is isolated by amplifying by PCR using the above plasmid pCH102 which is prepared from E. coli deposited under Budapest Treaty with NIBH of 1-1-3, Higashi, Tsukuba-shi, Ibaraki-ken, Japan, under the accession number of ERM BP-2800 (date of original deposit: May 12, 1989) as a template and the primers CS1-S (the nucleotide sequence is represented by SEQ. ID NO. 9 of the Sequence Listing) and M4, and then digesting with the restriction enzymes NheI and SalI.
On the other hand, a DNA fragment is isolated by amplifying by PCR using the plasmid pTF7520ColV, which contains a gene encoding C277-ColV and prepared from above E. coli FERM BP-5277 as a template and the primers CF and CNR, and then digesting with the restriction enzymes AccIII and NheI. The nucleotide sequences of CF and CNR are represented by SEQ. ID Nos. 10 and 12 of the Sequence Listing. The above two DNA fragments are mixed and ligated with an about 4.4 kb DNA fragment obtained by digesting the plasmid pTF7520ColV with the restriction enzymes AccIII and SalI. The resultant plasmid encodes the polypeptide C-ColV-CS1 which has CS-1 cell adhesion domain at the C-terminal of C277-ColV and in which the second glutamic acid from the C-terminal of ColV and the C-terminal threonine are replaced by alanine and serine, respectively. After culture of E. coli transformed with this plasmid, the desired polypeptide can be obtained from the culture. This C-ColV-CS1 is particularly useful in gene transfer into a target cell having CS1 binding property, especially, stem cells.
As the polylysine, as described above, that having a suitable polymerization degree can be selected from commercially available polylysines and used.
The functional materials to be used in the present invention can include derivatives of the above functional materials. Examples thereof include the above C-FGF-CS1 or its functional equivalents and C-ColV-CS1 or its functional equivalents. In addition, polymers obtained by polymerizing plural molecules of the functional materials and modified materials obtained by modifying the functional materials according to known methods (addition of sugar chain, etc.) can also be used in the present invention. These polymers and their functional equivalents can be prepared by genetic engineering techniques using genes encoding the polymers and genes encoding their functional equivalents. In addition, a cysteine-added functional material useful for preparing a polymer of the functional material can be prepared by addition, insertion and substitution of cysteine in the amino acid sequence of the functional material. In addition, a molecule which is a cysteine-added functional material and has a retrovirus binding domain is readily coupled to an another molecule which is a cysteine-added functional material and has a target cell binding domain. Furthermore, a material coupled to other functional material can be prepared by utilizing the reactivity of the cysteine residue of the cysteine-added functional material.
In another preferred aspect of the present invention, gene transfer is carried out by using a polymer of the retrovirus binding domain of fibronectin which increases the gene transfer efficiency into target cells with retroviruses.
The functional material is a polypeptide having plural Heparin-II binding domains of human fibronectin in one molecule as described in the above WO 95/26200 or derivatives of the polypeptide. In so far as the same activity as that of the functional material is maintained, functional equivalents a part of whose amino acid sequences are different from that of the naturally occurring products can be included.
Examples of the polymer of the functional material include those obtained by enzymologically or chemically polymerizing the above polypeptide derived from fibronectin or by gene engineering techniques. An example of a polypeptide which has two Heparin-II binding domains derived from fibronectin in a molecule include a polypeptide having an amino acid sequence represented by SEQ. ID No. 13 of the Sequence Listing (hereinafter referred to as H2-547). H2-547 can be obtained according to the method described herein by using E. coli which has been deposited under Budapest Treaty with NIBH of 1-1-3, Higashi, Tsukuba-shi, Ibaraki-ken, Japan, under the accession number of FERM BP-5656 (date of original deposit: Sep. 6, 1996). A polypeptide having an amino acid sequence represented by SEQ. ID No. 14 of the Sequence Listing is a polypeptide derivative containing a cell adhesion polypeptide of fironectin coupled at the N-terminal of H2-547 (hereinafter referred to as CH 2-826). This polypeptide can be obtained according to the method disclosed herein. Further, a polypeptide having an amino acid sequence represented by SEQ. ID No. 30 of the Sequencing Listing is a polypeptide derivative containing CS-1 cell adhesion region of fibronectin coupled at the C-terminal of H2-547 (hereinafter referred to as H2S-573). The polypeptide can be obtained according to the method described herein by using E. coli which has been deposited under Budapest Treaty with NIBH of 1-1-3, Higashi, Tsukuba-shi, Ibaraki-ken, Japan, under the accession number of FERM BP-5655 (date of original deposit: Sep. 6, 1996). H2S-573 having CS-1 cell adhesion region is useful for gene transfer into hematopoietic stem cells.
In yet another preferred aspect of the present invention, viable target cells are infected with a replication deficient retroviral vector in the presence of the functional material immobilized on beads which is effective to increase the gene transfer efficiency into cells with a retroviral vector.
Conventional methods for improving the gene transfer efficiency into target cells with a retroviral vector by using the functional materials described in the above WO 95/26200 and Nature Medicine are carried out by immobilizing the functional materials on a vessel to be used for infection of cells with viruses (a plate for cell culture). These methods require complicated procedures such as washing of excess functional material after treatment of the plate with a solution containing the functional material.
Then, the gene transfer methods using a plate having the functional materials immobilized thereon are hardly to say a convenient method. On the other hand, a method using the functional materials immobilized on bead(s) has the following advantages.
In comparison with a plate, immobilization on beads can be carried out at a relatively small space and beads can be handled in a sealed vessel. Since a surface of a plate having the functional material immobilized thereon is exposed to air, it is necessary to take care to prevent deterioration or the like due to drying during storage in case the functional material having lower stability. However, beads can be stored by suspending in a solution and such troubles can be avoided. Moreover, a surface area of the functional material becomes larger by using beads and therefore, in comparison with a plate, the higher gene transfer efficiency can be obtained.
Immobilization of the functional materials can be carried out by the conventional method, for example, a target cell culture vessel is coated with the functional materials or the functional materials can be immobilized, for example, on culture beads for culturing cells. The raw material and kind of beads can be selected depending upon the intended use. For example, the bead may have a circular or spherical core as a central portion and the surface of the core can be coated with a hydrophilic polymer. Examples of the raw material and the kind of the core and the polymer are described in JP-A 8-501092. For example, biodegradable beads on which these functional materials are immobilized may be administered in a living body. Alternatively, an effective method is to use a mixture of beads on which a molecule having a retrovirus binding domain is immobilized and beads on which a molecule having a target cell binding domain is immobilized.
When these functional materials are used without immobilization, for example, a target cell culture vessel can be pre-treated with a substance which prevents the functional materials from the adhesion to the vessel, for example, bovine serum albumin (BSA). Thus, the functional materials can be used without non-specific adhesion to the vessel.
According to the present invention, gene transfer can be efficiently carried out even in such a system that the functional material of the present invention is used without immobilization.
In addition, by using the target kit specifically designed for carrying out the method of the present invention as described hereinafter, gene transfer into cells can be very conveniently carried out.
As described above, transformant cells obtained according to the method of the present invention can be grafted into a living body, thereby gene therapy can be carried out to express an exogenous gene in a living body.
For example, when hematopoietic stem cells are used as target cells, gene therapy can be carried out by the following procedures. First, a material containing the hematopoietic cells, for example, bone marrow tissue, peripheral blood, fetal umbilical cord blood or the like is collected from a donor. The material can be used as such. However, usually, a monocyte fraction containing hematopoietic stem cells is prepared by density gradient centrifugation or the like. Alternatively, hematopoietic stem cells can be purified by utilizing markers on cell surfaces such as CD34 and/or c-kit. The material containing hematopoietic cells can optionally be pre-stimulated with a suitable cell growth factor or the like and then, the cells are infected with a recombinant retroviral vector into which an intended gene has been inserted according to the method of the present invention, in particular, in the presence of the functional material having stem cell binding activity. The transformant cells thus obtained can be grafted into a recipient by, for example, intravenous administration. The recipient is, preferably, an autologous donor but also including allogeneic transplants, the latter especially where umbilical core blood cells are used for the graft.
Gene therapy using hematopoietic stem cells as target cells is to compensate for a deficient or abnormal gene of a patient and examples thereof include ADA deficiency and Gaucher""s disease. In addition, sometimes, transduction of a drug resistant gene is carried out to relieve hematopoietic stem cell disorders due to chemotherapy used in treatment of cancers, leukemias and the like.
It has been known that hematopoietic stem cells express VLA-4 receptor and it is therefore possible to carry out gene transfer efficiently by using the functional material having CS-1 cell adhesion region disclosed by the present invention. Further, as described above, molecules such as CD34 and c-kit are expressed on the surface of hematopoietic stem cells and therefore the gene transfer efficiency can be improved by combining antibodies against to these molecules or a stem cell factor which is a ligand of c-kit with the functional material having retrovirus binding domain.
Moreover, as gene therapy of cancers, tumor vaccino-therapeutics have been studied, wherein cytokine genes are transferred into cancer cells and, after depriving growth capability, the cells are returned to the present body to increase tumor immunity (Human Gene Therapy, Vol. 5, pp. 153-164 (1994)). Such treatment can also be carried out effectively by applying the method of the present invention with the functional material having high affinity to cancer cells.
Further, activities have been attempted to treat AIDS by gene therapy. In this case, it has been proposed to transfer a gene encoding a nucleic acid molecule which inhibits HIV replication or gene expression (e.g., anti-sense nucleic acid, ribozyme, etc.) into T cells which is infected with HIV which causes AIDS (J. Virol., Vol. 69, pp. 4045-4052 (1995)). Gene transfer into T cells can be achieved by the method of the present invention with utilizing the functional material, for example, CD4 antibody or the like which can bind to a molecule present on the surface of T cells.
Thus, as target cells for gene transfer, any cells can be used in so far as the functional material having target cell binding domain of the present invention is available or can be prepared.
Moreover, the method of the present invention is suitable for protocols of clinical gene therapy because co-cultivation of target cells in the presence of retrovirus producer cells is not required and the method of the present invention can be carried out in the absence of hexadimethrine bromide whose use is clinically disadvantageous in human being.
Further, as application of the present invention to art fields other than gene therapy, for example, transgenic vertebrate animals can be simply produced by using, as a target cells, embryoplastic stem cells, primordial germ cell, oocyte, oogonia, ova, spermatocyte, sperm and the like.
That is, as one aspect, the present invention provides a method for cellular grafting comprising grafting the transformant cells obtained by the method of the present invention into a vertebrate animal. Examples of vertebrate animals to be grafted with transformant cells include mammals (e.g., mouse, rat, rabbit, goat, pig, horse, dog, monkey, chimpanzee, human being, etc.), birds (e.g., chicken, turkey, quail, duck, wild duck, etc.), reptiles (e.g., snake, alligator, tortoise, etc.), amphibian (e.g., frog, salamander, newt, etc.), fishes (e.g., dog mackerel, mackerel, bass, snapper, grouper, yellowtail, tuna, salmon, trout, carp, sweetfish, eel, flounder, shark, ray, sturgeon, etc.).
Thus, according to this aspect of the present invention, like substantially pure fibronectin, substantially pure fibronectin fragments or a mixture thereof, gene transfer with retorviruses can be carried out efficiently by the retrovirus binding domain and the target cell binding domain of the functional material to be used in the present invention. Then, the present invention can provide a technique for transferring genetic materials into vertebrate cells without any limitation of conventional techniques.
In a further aspect of the present invention, an effective amount of a material which has been retrovirus binding domain and target cell binding domain on the same molecule and has functions equivalent to those of substantially pure fibronectin, substantially pure fibronectin fragments or a mixture thereof is used as the functional material.
Such a functional material is a material which can perform gene transfer with the same efficiency as that of fibronectin, a fibronectin fragment or a mixture thereof. Typically, it is the functional material having the above novel retrovirus binding domain and target cell binding domain of the present invention on the same molecule. In case of using these materials, it is considered that retroviruses as well as target cells bind to at least one functional material.
Examples of the functional material having a retrovirus binding domain and a target binding domain on the same molecule include polypeptides represented by SEQ. ID Nos. 21 and 22 of the Sequence Listing (hereinafter referred to as CHV-181 and CHV-179, respectively).
These peptides include type III similar sequences (III-12, III-13 and III-14) contained in H-271. In CHV-181, III-12 and III-13 sequences, and in CHV-179, III-13 and III-14 sequences are added to the C-terminal of the cell adhesion polypeptide (Pro1239-Ser1515) of fibronectin via methionine. A plasmid for expressing the polypeptide CHV-181 can be constructed, for example, by the following procedures.
First, the plasmid pHD101 containing a DNA fragment encoding the heparin binding polypeptide (H-271) of fibronectin is prepared in Escherichia coli HB101/pHD101 (FERM BP-2264). A HindIII site is introduced in a region encoding the C-terminal of the III-13 sequence on this plasmid by site-directed mutagenesis, followed by digestion with NcoI and HindIII to obtain a DNA fragment encoding III-12 and III-13 sequence. On the other hand, the plasmid vector pINIII-ompA1 is digested with HindIII and SalI to obtain a DNA fragment encoding a lipoprotein terminator region.
Next, the plasmid pTF7021 containing a DNA fragment encoding the cell adhesion polypeptide (C-279) of fibronectin is prepared from Escherichia coli JM109/pTF7021 (FERM BP-1941), and a NcoI site is introduced immediately before termination codon of C-279 on the plamsid by site-directed mutagenesis to obtain the plasmid pTF7520. This plasmid is digested with NcoI and SalI, followed by mixing with the DNA fragment encoding the III-12 and III-13 sequence and the DNA fragment encoding a lipoprotein terminator region to ligate them to obtain the plasmid pCHV181 for expressing the polypeptide CHV-181. The nucleotide sequence of a region encoding the polypeptide CHV-181 on the plasmid pCHV181 is shown in SEQ. ID No. 27 of the Sequence Listing.
A plasmid for expressing the polypeptide CHV-179 can be constructed, for example, by the following procedures.
First, a NcoI site is introduced in a region encoding the N-terminal of the III-13 sequence on the plasmid pHD101 by site-directed mutagenesis, followed by digestion with NcoI and HindIII to obtain a DNA fragment encoding the III-13 and III-14 sequence. This is mixed with a DNA fragment encoding the above lipoprotein terminator region and the NcoI and SalI-digested plasmid pTF7520 to ligate them to obtain the plasmid pCHV179 for expressing the polypeptide CHV-179.
CHV-181 and CHV-179 can be obtained by culturing E. coli transformed with the above plasmids, respectively, then purifying from the resulting culture.
These functional materials can be used by immobilized on, for example, beads as described above or without immobilization.
In another aspect, the present invention provides a culture medium of target cells to be used for gene transfer into the target cells with retroviruses which comprises (1) the above-described mixture of an effective amount of the functional material having retrovirus binding domain and an effective amount of another functional material having the target cell binding domain or (2) an effective amount of the functional material having the above described novel retrovirus binding domain and target cell binding domain on the same molecule. The functional material may be immobilized or may be used without immobilization.
Other ingredients of the culture medium of the present invention are not specifically limited in so far as they can be used in culture of target cells and commercially available culture mediums for culturing cells can be used. The culture medium of the present invention can also contain serum, a cell growth factor necessary for growth of target cells, an antibiotic for preventing contamination of microorganisms and the like. For example, in case of NIH/3T3 cell, Dulbecco""s modified Eagle""s medium (DMEM, JRH Bioscience) containing 10% bovine fetal serum (Gibco), 50 units/ml of penicillin and 50 xcexcg/ml of streptomycin (both Gibco) can be used as the culture medium.
In further aspect, the present invention provides a method for localization of a retrovirus which comprises incubating a culture medium containing the retrovirus contacted with (1) the above-described mixture of a molecule containing the retrovirus binding domain and another molecule containing the target cell binding domain, (2) the above-described functional material having the novel retrovirus binding domain of the present invention and a target cell binding domain on the same molecule, or (3) the above-described functional material having the retrovirus binding domain.
As described above, the functional material may be immobilized or may be used without immobilization. Incubation can be carried out according to a conventional method, for example, a 37xc2x0 C. under the conditions of CO2 concentration of 5% and humidity of 99.5%. These conditions can be suitably adjusted depending on particular target cells to be used and the culture period can also be changed according to particular cells and purposes.
By using the method of the present invention, viral particles can be localized in various constructs which deliver viruses into target cells.
In another aspect of the present invention, there is provided a kit for using retrovirus-mediated gene transfer into target cells. The kit comprises:
(a) an effective amount of (1) a mixture of the molecule having the above described retrovirus binding domain and another molecule having the target cell binding domain, or (2) the functional material having the novel retrovirus binding domain of the present invention and the target cell binding domain on the same molecule;
(b) an artificial substrate for incubating the retrovirus contacted with the target cells; and
(c) a target cell growth factor for pre-stimulating the target cells. The functional material (a) may be immobilized or non-immobilized. This kit may further comprise a recombinant retroviral vector, necessary buffers and the like.
As the artificial substrate, there can be used plates for culturing cells, petri dishes, flasks and the like. They may be made of polystyrene.
In case that target cells are cells in G0 phase, infection with a retrovirus does not occur and therefore, preferably, cells are pre-stimulated to lead cells to the cell cycle. For this purpose, target cells are cultured in the presence of a suitable cell growth factor prior to infection with a retrovirus. For example, in case of gene transfer into bone marrow cells and hematopoietic stem cells, a target cell growth factor such as Interleukin-6 or a stem cell factor can be used.
Respective constituent members of the kit can be prepared in the form of freeze dried products, granules, tablets in addition to aqueous solutions according to per se known methods.
By using the kit of the present invention, for example, a transformed viable target cell culture can be obtained and retrovirus-mediated transduction into target cells can be simply carried out.
The present invention also includes a method for gene transfer into target cells with retrovirus wherein the functional material selected from the group consisting of substantially pure fibronectin, substantially pure fibronectin fragments and a mixture thereof, or a polymer thereof which is immobilized on beads or not immobilized is used.
The present invention includes the above described CH2-826 and its functional equivalents. In addition, the present invention provides a gene encoding CH2-826. One example thereof is a gene represented by SEQ. ID No. 20 of the Sequence Listing. The present invention also includes functional equivalents of the gene.
Further, the present invention provides the above described CHV-181 and includes its functional equivalents. In addition, the present invention provides a gene encoding CHV-181. One example of the gene is that represented by SEQ. ID No. 27 of the Sequence Listing. The present invention also includes functional equivalents of the gene.
The present invention also provides a polymer containing a polymer of the retrovirus binding domain and/or a polymer of the target cell binding domain. Specific examples of the polymer are a polymer of a fibroblast growth factor and a polymer of a polypeptide having an insulin binding domain derived from type V collagen.
As discussed hereinafter, although the present invention is not limited to any theory, it is believed that gene transfer into cells with a retrovirus, i.e., transformation is enhanced by binding the retrovirus and the target cell to respective functional domains.
As such a functional material which binds to a retrovirus and thus is useful in the present invention, there are substantially pure fibronectin, substantially pure fibronectin fragments or a mixture thereof. The present inventors have found that the above-described functional materials of the present invention having functions substantially the same as those of substantially pure fibronectin and the like improve the gene transfer efficiency, i.e., the transformation efficiency of target cells with a retrovirus.
The fragments of fibronectin described herein may be of natural or synthetic origin and can be prepared in substantial purity from naturally occurring materials, for example as previously described by Ruoslahti et al. (1981) J. Biol. Chem. 256:7277; Patel and Lodish (1986) J. Cell. Biol. 102:449; and Bernardi et al. (1987) J. Cell. Biol. 105:489. In this regard, reference herein to substantially pure fibronectin or a fibronectin fragment is intended to mean that they are essentially free from other proteins with which fibronectin naturally occurs.
The substantially pure fibronectin or fibronectin fragment described herein can also be produced by genetic engineering techniques, for example, as generally described in U.S. Pat. No. 5,198,423. In particular, the recombinant fragments identified in the Examples below as H-271, H-296, CH-271 (SEQ ID NO 23) and CH-296 (SEQ ID NO 24), and methods for obtaining them, are described in detail in this patent. The C-274 fragment used in the Examples below was obtained as described in U.S. Pat. No. 5,102,988. These fragments or fragments from which they can be routinely derived are available by culturing E. coli deposited with NIBH of 1-1-3, Higashi, Tsukuba-sh, Ibaraki-ken, Japan under Budapest Treat with the accession numbers of FERM P-10721 (H-296) (the date of original deposit: May 12, 1989), FERM BP-2799 (C-277 bound to H-271 via methionine) (the date of original deposit: May 12, 1989), FERM BP-2800 (C-277 bound to H-296 via methionine) (the date of original deposit: May 12, 1989) and FERM BP-2264 (H-271) (the date of original deposit: Jan. 30, 1989), as also described in U.S. Pat. No. 5,198,423.
In addition, useful information as to fibronectin fragments utilizable herein or as to starting materials for such fragments may be found in Kimizuka et al., J. Biochem. 110, 284-291 (1991), which reports further so as to above-described recombinant fragments; in EMBO J., 4, 1755-1759 (1985), which reports the structure of the human fibronectin gene; and in Biochemistry, 25, 4936-4941 (1986), which reports on the Heparin-II binding domain of human fibronectin. Fibronectin fragments which contain both the CS-1 cell adhesion domain and the Heparin-II binding domain have been found to significantly enhance the efficiency of gene transfer into hematopoietic cells in work thus far.
It will thus be understood that the fibronectin-related polypeptides described herein will provide an amino acid sequence having the cell-binding activity of the CS-1 cell adhesion domain of fibronectin as well as an amino acid sequence of the Heparin-II binding domain of fibronectin which binds the virus.
The viral-binding polypeptide utilized to enhance transduction by retroviral vectors as disclosed in WO 95/26200 will comprise (i) a first amino acid sequence which corresponds to the Ala1690-Thr1960 of the Heparin-II binding domain of human fibronectin, which is represented by the formula (SEQ ID NO 1):
or a sufficiently similar amino acid sequence thereto to exhibit the ability to bind the retrovirus; and (ii) a second amino acid sequence (CS-1) which corresponds to one portion of the IIICs binding domain of human fibronectin; which is represented by the formula (SEQ. ID No. 2):
Asp Glu Leu Pro Gln Leu Val Thr Leu Pro His Pro Asn Leu His Gly Pro Glu Ile Leu Asp Val Pro Ser Thr;
or a sufficiently similar amino acid sequence thereto to exhibit the ability to bind hematopoietic cells such as primitive progenitor and/or long term repopulating (stem) cells.
The retrovirus binding activity of a polypeptide represented by the above SEQ. ID No. 1 (H-271) shows a concentration dependence and, as indicated in Example 8 below, it shows substantially the same activity as that of CH-271 at high concentrations. That is, a retrovirus and target cells bind to at least one molecule of H-271 for the first time in the presence of a high concentration of H-271.
The strong virus binding to the virus binding domain of the functional material of the present invention can be used for constructing delivery systems for virus-mediated therapy across a broad range of cell types. For this purpose, a polypeptide containing the retrovirus binding domain of the functional material of the present invention can be coupled to any material containing a cell binding domain which gives this construct specificity for the target cells, or can be co-localized with a material containing its cell binding domain. That is, the virus binding polypeptide may be covalently coupled to the cell binding material or they may be different molecules.
This approach will circumvent the prior necessity of constructing specific retrovirus cell lines for each target cell and facilitate selection of the functional material having the most suitable target cell binding domain according to a particular kind of target cells. Therefore, by using the functional material of the present invention, transduction specific for target cells to be used can be readily carried out and, in particular, the method of the present invention wherein a mixture of the functional material having retrovirus binding domain and the functional material having target cell binding domain is especially useful for transfer the required gene into the intended target cell. In addition, the novel functional material provided by the present invention is especially useful for the method for improving the gene transfer efficiency into target cells with retroviruses and related techniques.
The following Examples further illustrate the present invention in detail but are not to be construed to limit the scope thereof.